NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Doug Royer
Date: 2007 May 4, 10:42 -0700
General question to the list:
It is common practice to check for IC before and after a
round of sights. In my experience, they are seldom the same particularly when
taking sights under non-standard temperatures.
Question: what correction would you apply? Generally
what I do is a combination of fudging and black magic but it usually entails
simply taking the two ICs and averaging them to arrive at a single IC that can
be applied to the entire round of sights.
Please: I am not looking for involved statistical
computations. I am trying to determine what other navigators do in the field/at
sea.
cheers,
Robert
Well Robert, this is what I usually
do for a round of sights.
Check the index error at some point before
the round or single sight begins. The closer to the time of cuts the better. Then
take the sights needed in the round and apply the correction. Some sextants are
more prone than others to shifts in index error caused by environmental
conditions in my experience. Over time of using a certain sextant one gets a “feel”
for knowing when to be especially concerned or vigilant about checking for a
more than “normal” increase in the sextant’s error. Not very
scientific but just something I’ve learned from experience. My Tamaya
holds it’s error fairly steady over a wide range of temps and humidity
over many years.
Close enough for gubment work so to speak.
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